This invention relates to electroluminescent phosphor compositions that may be used for AC Thin Film Electroluminescent (ACTFEL) devices. This invention also relates to a crystal engineering method that allows chromatic control of phosphor emission across the visible spectrum. The invention further relates to luminescent devices produced from such phosphor compositions.
Commercial electroluminescent (EL) devices are desirable for their wide viewing angles, crisp resolution, high contrast ratios, and durability. However, monochrome output and the unavailability of a suitable red-green-blue phosphor set have hampered widespread utility of electroluminescent devices.
At present, commercial flat-panel EL devices operate on the basis of the amber emission from thin films of the phosphor ZnS:Mn. In order to realize full color output, suitable phosphors broadly emitting in the blue and yellow portions of the spectrum can be combined to produce a solid-state EL source of white light. The white emission from such phosphor combinations is then passed through appropriate color shutters. The drawback to this technique is that the light is greatly attenuated by passage through such shutters. In order to replicate the performance of a cathode-ray tube, it would be advantageous to provide efficient EL-active red, green, and blue phosphors having specific chromaticity values.
The phosphor compositions described herein provide efficient, electroluminescently active phosphors that may be used to provide a phosphor set that is substantially red, green, blue.
The crystal engineering methods of the invention provide chromaticity control that may be used to provide a highly efficient red, green, and blue phosphor set for electroluminescence applications.
A phosphor material is of the formula Zn1-3x/2MxX:Mn, wherein M is selected from the group consisting of the trivalent cations of Al, In, Ga, and mixtures thereof, and X is selected from the group consisting of S, Se, Te, and mixtures thereof. Most advantageously X is sulfur. The phosphor material exhibits a systematic red shift of its emission as x varies from 0.01 to 0.49. The amount of Mn can be 0.5 to 5.0 mol %, but control of the emission maximum is achieved by changing the amount of trivalent cation. The phosphor material can be used in a variety of electroluminescent devices.
Another phosphor material is of the formula MX:Cu, L, A wherein M is selected from the divalent ions of Sr, Mg, Ca, Ba, and mixtures thereof, X is selected from the group consisting of S, Se, Te, and mixtures thereof, L is selected from the group consisting of the trivalent cations of the lanthanides, Al, In, Ga, Sc, and mixtures thereof, and A is selected from the group consisting of the alkali metal ions and mixtures thereof. Most advantageously, X is sulfur and L is selected from the group consisting of the trivalent lanthanide cations and mixtures thereof. This phosphor material undergoes a systematic blue shift in its emission maximum as the amount of L is increased from 0.05 to 5 mol % and undergoes a systematic red shift as the amount of A is increased from 0.05 to 5 mol %. The amount of copper can vary from 0.05 to 5.0 mol % copper, but need not be changed in order to vary the emission maximum. In a particular embodiment the combined amount of L and A is equal to the amount of copper. This phosphor material can also be used in luminescent devices.
Advantageously a luminescent device includes both a phosphor material of he formula Zn1-3x/2MxX:Mn and a phosphor material of the formula MX:Cu, L, A.
A luminescent device can be made by providing a suitable substrate and applying to the substrate at least one phosphor material selected from the group consisting of phosphor materials of the formula Zn1-3x/2MxX:Mn and phosphor materials of the formula, MX:Cu, L, A.